The invention relates to a vehicle sensor for detecting impact sound comprising a measured-value sensor (4.1) for detecting an impact sound, the measured-value sensor (4.1) comprising several individual, separate measured-value sensing elements (4.1.x), each of which is coupled to a vehicle structure (5) in such a way that impact sound waves are transmitted by the vehicle structure (5) to the measured-value sensing elements (4.1.x), characterized in that the measured-value sensor is a piezoelectric, piezoresistive or capacitive measured-value sensor and that the individual, separate measured-value sensing elements are arranged as electrodes in a two-dimensional form in the measured-value sensor.
It is known that oscillations in the body of a motor vehicle, which are caused for instance by a crash, can be detected by means of an impact sound sensor. For optimally adapting passenger protection to different driving situations, the impact sound sensors are fixed directly outside at the vehicle body or are also arranged in the control unit, as far as it is coupled to the vehicle body with regard to oscillation. Fixing the sensors outside at the vehicle body as lateral or upfront sensors is advantageous in case of a side crash or a crash with an obstacle of small mass, as it enables fast and safe recognition of an accident and thus the efficient application of protection means.
Known apparatuses for triggering safety devices in a vehicle are often equipped with several sensors for detecting impact sound or acceleration. If the sensors are able to detect acceleration of a vehicle and the impact sound simultaneously, the signal portions of acceleration and impact sound as a rule have to be filtered out from the wideband signal by means of a downstream processing unit at high expenditure. In doing so, either digital filters are used, which require a preceding A/D-conversion of the sensor signal or analogous filters are used, the use of which is mostly still more expensive than the use of digital filters. Moreover, the sensors frequently have a different sensitivity direction when it comes to the detection of acceleration or impact sound. Therefore, in a safety device mostly several of these sensors are used.
For instance from U.S. Pat. No. 6,595,544 B1 consideration of acceleration and impact sound signals by means of a sensor is known.
Beyond that, from DE 3703946 a frequency-selective oscillation sensor with a plurality of movable tongues is formed out of a substrate, the tongues being arranged in a row and comprising different lengths, so that each tongue has a different self-resonant frequency and thus is sensitive to a defined frequency region.
WO 03/062780 shows an omni-directional crash sensor, from which preferably a plurality is to be arranged distributed on the windshield to determine in addition to the strength of the crash also from geometrical calculations the direction of the crash.
It is now the object of the present invention to propose a vehicle sensor for detecting impact sound, which enables a simple and exact detection of signal portions of the impact sound and if necessary of acceleration, in order to ensure for instance triggering of a safety device in a vehicle with a preferably low number of sensors.